netdev - Re: [PATCH v2 bpf-next 0/5] Bitfield and size relocations support in libbpf

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Date:   Mon, 4 Nov 2019 16:38:41 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Andrii Nakryiko <andriin@...com>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, ast@...com, yhs@...com
Cc:     andrii.nakryiko@...il.com, kernel-team@...com
Subject: Re: [PATCH v2 bpf-next 0/5] Bitfield and size relocations support in
 libbpf

On 11/1/19 11:28 PM, Andrii Nakryiko wrote:
> This patch set adds support for reading bitfields in a relocatable manner
> through a set of relocations emitted by Clang, corresponding libbpf support
> for those relocations, as well as abstracting details into
> BPF_CORE_READ_BITFIELD/BPF_CORE_READ_BITFIELD_PROBED macro.
> 
> We also add support for capturing relocatable field size, so that BPF program
> code can adjust its logic to actual amount of data it needs to operate on,
> even if it changes between kernels. New convenience macro is added to
> bpf_core_read.h (bpf_core_field_size(), in the same family of macro as
> bpf_core_read() and bpf_core_field_exists()). Corresponding set of selftests
> are added to excercise this logic and validate correctness in a variety of
> scenarios.
> 
> Some of the overly strict logic of matching fields is relaxed to support wider
> variety of scenarios. See patch #1 for that.
> 
> Patch #1 removes few overly strict test cases.
> Patch #2 adds support for bitfield-related relocations.
> Patch #3 adds some further adjustments to support generic field size
> relocations and introduces bpf_core_field_size() macro.
> Patch #4 tests bitfield reading.
> Patch #5 tests field size relocations.
> 
> v1->v2:
> - added direct memory read-based macro and tests for bitfield reads.

Applied, thanks!